Conventional thrust-bearing apparatuses and radial bearing apparatuses may comprise bearing elements including bearing surfaces that at least partially contact and move or slide relative to one another during use. Such bearing elements may include a superhard material (e.g., polycrystalline diamond) for resisting wear during use of the bearing apparatus.
One application for bearing apparatuses is in a subterranean drilling system configured to drill a borehole into a subterranean formation for oil or gas exploration. In a typical subterranean drilling system, a downhole drilling motor is suspended at the lower end of a drill string of drill pipe comprising a series of connected pipe sections. A rotary drill bit (e.g., a fixed cutter drill bit, roller cone drill bit, a reamer, etc.) may be supported below the drilling motor (via pipe sections, drill collars, or other structural members) or may be directly connected to the downhole motor. Drilling fluid (also commonly known as drilling mud) may be circulated through the drill string and the downhole drilling motor to generate torque therewithin to rotate the rotary drill bit and drill a borehole in the subterranean formation. During drilling, the drilling fluid may be returned to the surface through the annular space between the drilled borehole and the drill string and may carry the cuttings of the subterranean formation to the surface. Thrust-bearing apparatuses may be employed in the subterranean drilling system for carrying thrust loads generated during the drilling process.
Radial bearing apparatuses are used in conventional downhole drilling components, such as roller cones. Such radial bearing apparatuses include an inner and outer race, each which may include a plurality of superhard bearing elements (e.g., polycrystalline diamond compacts). The races are positioned adjacent one another so that bearing surfaces of the bearing elements contact one another during use. For example, the inner race may be mounted or affixed to a spindle of a roller cone and the outer race may be affixed to an inner bore formed within the roller cone to enable rotation of the roller cone.